Single reel data tape cartridges, one generation of which is known as 3480 type cartridges, include a reel containing magnetic tape with a leader block attached to the free end of the tape as it extends from the reel. The cartridge is generally rectangular except for one corner which is angled and includes a leader block window. The leader block window holds the leader block and permits the tape to exit from the cartridge for threading through a tape drive when the leader block is removed. When the leader block is snapped into the window, the window is covered.
The leader block is generally rectangular and has a cutout which combines with a pin to hold the tape. The front surface of the leader block includes a slot for engaging an automatic threading apparatus in a reel-to-reel magnetic tape drive apparatus. The front surface of the leader block is generally cylindrical and has a rounded boss which engages with an inclined surface of the corner of the cartridge. The rear surface is rounded to form a portion of an arc of a radius to match the periphery of the take-up reel hub in the tape drive apparatus as the leader block fits into the slot in the hub. A compliant section may be formed on the leader block to permit the leader block to compress at its rear surface to accommodate especially the first layer of tape when the tape is wound onto the take-up reel.
The tape drive apparatus includes a threading apparatus for connection to a single reel tape cartridge. The drive apparatus includes a drive motor for the supply reel mounted beneath a base plate so that its shaft extends normal to and slightly above a surface of the base plate. A take-up reel is mounted on the base plate and is attached to the motor. The cartridge reel, when coupled to the motor, lies in substantially the same plane as a hub of the take-up reel so that the tape moves in a plane normal to both motor shafts when being transported. After the threading of the tape, transfer of the tape between the supply reel and the take-up reel is achieved by controlling the driving motors for the reels. The tape passes through a vacuum guide, a magnetic transducer head, and a tension transducer.
Known tape reels for single reel cartridges are used with half inch tape which has a nominal width of 1.265 cm (0.498 in). These reels typically have a cylindrical hub and a flange located on each axial end of the hub. The hub includes a cylindrical tape winding surface which extends between the two ends. The hub and lower flange are typically molded as a single piece and the upper flange is welded onto the hub, generally using sonic welding to create the weld. A collapsing weld joint is used and is located between the top surface of the hub and the bottom surface of the upper flange. Spacing of the upper flange with respect to the hub datum (the pitch line of the hub teeth) varies and the amount of wobble in the upper flange varies depending on the amount that the weld bead collapses and the uniformity of collapse during welding. While these variations are within acceptable limits, there is a need for a weld design which produces a more uniform spacing between the flanges and less wobble variation.